Marker tracking systems in general are used in medical technology to determine and track a position of treatment-assisting apparatus, instruments and/or parts of the patient's body. Using the positional data for the instruments, it is possible to perform medical navigation to assist physicians in treating the patient. This enables image-guided surgery to be implemented, in which physicians can see and check the position or their instruments relative to the position of treatment targets (e.g., parts of the patient's body) via a screen output, even if parts of the instruments are no longer visible. This also enables and/or greatly simplifies the planning of incisions. The data on the patient's anatomy can be obtained from previously or intra-operatively ascertained detections using imaging methods, e.g., computer tomography, nuclear spin tomography, x-ray imaging, etc., and via a registration procedure, can be incorporated into a coordinate system of an operating theater and/or the instrument tracking system. DE 196 39 651, for example, describes a surgical navigation system comprising marker tracking.
While using a tracking system, it often happens (particularly in orthopaedic operations) that the marker quality is impaired because the markers become partially or completely occluded, e.g., when soiled with water, blood or other incidental liquids or solids. When markers fail or their quality is impaired, this impairs the functionality or accuracy of marker tracking.